Powdery Mildew - Knowledgebase Question

brownsburg, In
Avatar for l_edwards_17
Question by l_edwards_17
June 21, 2010
I have powdery mildew on my hydrangas and tall phlox. How can I kill this or treat it??? I just moved into the house and it was there when I moved in.
I also have a problem with the soil. The plants are a beautiful color when I buy them but after planting they lose their color. What do I need to add??? The soil is clay like.

Thanks Lora

Answer from NGA
June 21, 2010
Powdery mildew fungi spread quickest when the humidity is high and temperatures are between 50F and 90F. To discourage the disease, plant on sites with good air drainage, give the plants plenty of space, water during the morning only, and allow the soil to dry out between waterings. Remove any affected leaves, and if your plant is heavily covered with powdery mildew you should probably remove the entire plant so the infection doesn't spread. For heavy infestations of powdery mildew, sulfur or copper sprays can be applied weekly, starting in June in your area. These include: sulfur, neem oil (Rose Defense, Shield-All, Triact), triforine (Ortho Funginex), or potassium bicarbonate (Kaligreen, First Step) Chemicals are most effective when combined with cultural controls.

You can enrich your soil over a period of years by incorporating organic matter such as compost or aged manure. Spread some between the plants and dig it into the soil. Repeat each spring and you'll eventually end up with rich garden loam.

Best wishes with your landscape!

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